Want to insulate walls in my unfinished basement

I have an unfinished basement with the old clay red block foundation. I want to insulate the basement walls to help make the floors warmer upstairs. I already had the band joists spray-foamed.

I wanted to do this myself by purchasing some foam boards at a big box store and taping them at the seams.

My concern is about the moisture. My damp basement would be in the upper 70s or 80s in humidity % if I weren't running my dehumidifier constantly. If I put up these foam insulation boards, won't it trap moisture behind them and cause the foundation walls to rot and weaken?

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Want to insulate walls in my unfinished basement

You might want to check with your local building department as most codes are now requiring that foam insulatioin be covered with a ignition and thermal barrier. If this code exists in your area this would mean that you would have to cover the foam with some form of sheetrock or equivalent material to protect the foam adding an expense to the project.

If living floor warmth is your #1 goal, you may want to consider just insulating your floor joists. It would be cheaper and more efficient in the long run. Insulating just the basement walls would only solve a part of the basement heat loss as a relatively equal amount of heat is lost through the floor slab.

Want to insulate walls in my unfinished basement

"What kind of air sealing film or wrap should I be looking for to put over top of the insulation?"-------- no covering on the foam board. Tape the joints against air movement, canned foam the bottoms to the concrete.

Where are you located?

Describe the finished wall.....

Gary

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Want to insulate walls in my unfinished basement

Any foil-faced foam board is not recommended above grade on the basement walls to permit drying.

Gary

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